Hello, I hope you are doing well

If you have already been allotted a seat, the seat which you will get in extended round will depend upon your choice filling.

If the seat which you are gonna get in 2nd Extended round is better than your previous one or say it has higher preference in your choice filling, then your previous seat will be changed with the one you will get in 2nd Extended round, otherwise it will be retained.

Hope this helps.